Recording device, playback device and program

ABSTRACT

After sizes of Intra pictures included in a digital stream are detected, an analysis unit  6  totals numbers of occurrences of the Intra pictures for each size to obtain an occurrence distribution of the sizes of the Intra pictures. Values “000b” to “111b” are respectively assigned to distribution ranges of the sizes of the Intra pictures. Then, an entry map, in which each Intra picture is represented by one of the values “001b” to “111b”, are to be recorded onto a recording medium in association with the assignment information.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a technique for creating an entry map.

(2) Description of the Related Art

An entry map is information used for reading data at a certain locationin a data stream, where decoding can be started. For instance, an entrymap for a video indicates the address and the size of each I-picture(Intra picture). A technique for creating such an entry map is necessaryfor playing back a video stream that is encoded with use ofcorrelativity among frames, such as in MPEG-2 and MPEG-4 AVC, and thistechnique is adopted in BD-RE standard.

If the video stream is encoded by an encoding method such as MPEG2-Videoand MPEG4-AVC, it is compressed with use of correlativity among framesincluded in the stream, and accordingly the P-picture and the B-picturecan not be decoded unless the I-picture is decoded in advance.Therefore, a playback device reads an entry map, and interprets where tostart reading the data. The entry map enables the playback device toimmediately judge where, in the video stream, to start reading in orderto decode the I-picture firstly, without actually analyzing the contentof the stream. Using the entry map, it becomes possible to readI-pictures continuously without reading redundant data. This realizesspecial playback operations such as a playback at high speed and areverse playback in a suitable manner, even if the video stream isrecorded on a low-speed recording medium, such as an optical disc.

The following describes the entry map. The entry map includes entries,which are pieces of information about I-pictures included in the videostream. Each entry includes a pair of an I_start and an I_end.

The I_start is a relative address relative to the beginning of the videostream. The I_end is a 3-bit value showing the size of the I-picture.The size of the I-picture is represented by only 3-bit wide data,because a lot of I-pictures are included in the video stream and it isdemanded that data for each I-picture should be represented in a shortform.

SUMMARY OF THE INVENTION

The representation of the I-picture size using a 3-bit value isdescribed next. In the BD-RE, an average transmission rate of 24 Mbps isassigned to the video stream. Therefore, the I-picture size ispresumably within a certain range. Firstly, the I-picture size isdivided into seven ranges. Here, each of the seven ranges can berepresented by a 3-bit value (001b-111b). That is to say, the I-picturesize is represented by one of the numerical values representing thedivided ranges, namely the values 001b to 111b. This makes it possibleto represent the I-picture size by the 3-bit value.

By the way, this 3-bit representation is based on that the fluctuationband of the bit rates is narrow. This is because the BD-RE standardusing the entry map is designed for broadcast media, and there is noproblem assuming that the fluctuation band of the bit rates is narrow.However, the case is quite different if the video stream is providedfrom a package medium, such as a BD-ROM. Because, a variety of videos,from a main content of a movie of high quality to a video as an extrabonus of poor quality, are recorded together on a package medium. Thevideo stream is sometimes provided at a high transmission rate, forinstance at an average rate of 48 Mbps, and sometimes provided at a lowtransmission rate, for instance at an average rate of 1 Mbps, andtherefore the fluctuation band of the transmission rates is very wide.When the fluctuation band of the transmission rate is wide, the 3-bit ofthe I_end is not a sufficient bit width, and there is a problem that theI_end can not accurately represent the size of the I-picture.

The object of the present invention is to provide a recording devicethat can ensure efficient reading of I-pictures even in the case wherethe fluctuation band of the transmission rate for each video stream iswide.

The above object is fulfilled by a recording device that records adigital stream onto a recording medium, comprising: a detecting unitoperable to detect sizes of Intra pictures included in the digitalstream and output detected values including the Intra picture sizes; aclassifying unit operable to classify the detected values into N groups;an assigning unit operable to generate assignment information whichindicates distribution ranges of Intra picture sizes respectivelybelonging to the N groups in a one-to-one association with numericalvalues 1 to N respectively representing the N groups; and a recordingunit operable to record an entry map onto the recording medium inassociation with the assignment information, the entry map representingeach Intra picture included in the digital stream using the numericalvalues 1 to N.

The occurrence distribution of the Intra picture sizes changes as thebit rate of the digital stream changes. Therefore, the values areassigned to the distribution ranges of the Intra picture sizes. Byrecording information indicating the assignment, it becomes possible toknow which value represents which occurrence range at the time of theplayback.

BRIEF DESCRIPTION OF THE DRAWINGS

These and the other objects, advantages and features of the inventionwill become apparent from the following description thereof taken inconjunction with the accompanying drawings which illustrate a specificembodiment of the invention. In the drawings:

FIG. 1 shows a recording device 200 and a playback device 300 accordingto the present invention;

FIG. 2A shows an internal structure of an EP_map;

FIG. 2B shows functions of an I_start and an I_end in each entry;

FIG. 2C shows that only I-pictures are read from a video stream andplayed back;

FIG. 3 is an example graph showing occurrence rates of I-picturesincluded in a content, for each ECC block size;

FIG. 4A to FIG. 4D show how a playback device 300 interprets an I_end;

FIG. 5 is a graph showing occurrence distribution of I-picture sizes inthe case where a fluctuation band of assigned bit rates is wide;

FIG. 6 shows an internal structure of a recording device 200;

FIG. 7 is a flowchart showing a procedure performed by an analysis unit6 for creating an EP_map;

FIG. 8 is a flowchart showing a procedure for classifying measuredvalues;

FIG. 9 shows an example classification procedure performed in Step S12;

FIG. 10A to FIG. 10C show details of a conversion performed forconverting I-picture sizes into numbers of ECC blocks;

FIG. 11 shows an EP_map that is obtained by integrating an I_end_tableand a group of entries;

FIG. 12 shows an internal structure of playback device 300 according tothe present invention;

FIG. 13 shows a data structure of an EP_map according to the secondembodiment;

FIG. 14 shows an entry map according to the third embodiment;

FIG. 15 shows a group classification procedure according to the fourthembodiment:

FIG. 16A shows a relation between a number of ECC blocks representing anI-picture size and a number of I-pictures having the I-picture size;

FIG. 16B shows a result of a group classification performed in Step S16in FIG. 15;

FIG-17A is a coordinate system showing an occurrence distribution of anI-picture size;

FIG. 17B is a coordinate system, in which an occurrence distribution ofan I-picture size in FIG. 17A is classified into eight groups;

FIG. 18A is a coordinate system showing an occurrence distribution of anI-picture size, which is similar to FIG. 17A;

FIG. 18B is an example classification with consideration ofsingularities;

FIG. 19A shows how a range of an I-picture size is classified;

FIG. 19B shows a correlation among ranges of groups;

FIG. 19C shows that the measured values distributed as FIG. 19A showsare classified into eight groups;

FIG. 20 is a flowchart showing a procedure for classifying measuredvalues;

FIG. 21 shows specific examples of standard deviations calculated fortwo classification patterns;

FIG. 22 shows examples of assigned speed rates;

FIG. 23 shows a procedure for classifying measured values according tothe eighth embodiment; and

FIG. 24 describes a function of the classification performed in thetenth embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following describes a playback device according to preferredembodiments of the present invention. FIG. 1 shows a recording device200 and a playback device 300 according to the present invention.Firstly, a recording medium 100, which is to be subjected to a recordingby the recording device 200 and a playback by playback device 300, isdescribed.

Recording Medium 100

The recording medium 100 is used for recording an EP_map thereon inassociation with an AVClip. The AVClip is a multiplexed transport streamgenerated by multiplexing elementary streams, such as a video stream, anaudio stream and a graphics stream.

The EP_map is described next. FIG. 2A shows an internal structure of theEP_map. As shown in FIG. 2A, an entry map includes general information(EP_map_GI) and entries (Enry#1, . . . , Entry#k, . . . ) which arepieces of information about I-pictures. Each entry includes a pair of anI_start and an I_end. FIG. 25 shows functions of the I_start and theI_end included in each entry. In FIG. 2B, the lower figure represents avideo stream, and the upper figure represents a group of the entries.This video stream includes I-pictures, P-pictures and B-pictures. TheI_start included in each entry of the EP_map indicates a start positionof each I_picture (Address#1, #2). Each I_end has a 3-bit value thatindicates the size of each I_picture (001b, 010b). The start positionand the size of the I-picture is shown in each entry, and therefore itis possible to realize special playbacks, such as a playback at doublespeed (×2 speed) and a playback at triple speed (×3 speed), by readingonly the I-pictures from the video stream as shown in FIG. 2C.

Recording Device 200

The recording device 200 obtains the AVClip by performing an encodingbased on an audio input and a video input into the recording device 200itself. The recording device 200 also creates an EP_map corresponding tothe AVClip, and writes the AVClip together with the EP_map on therecording medium 100. Here, the recording device 200 records the groupof the entries such that the total size of the entries becomes small, byrepresenting the I-picture size within a short bit width.

The following describes the representation of the I-picture size by therecording device 200.

If the I-picture size is recorded byte-by-byte, it can be representedwith accuracy, and it is unnecessary to read redundant data for playingback only I-pictures continuously at a high speed. However, a largenumber of bits are required for recording the I-picture sizebyte-by-byte. For instance, if the maximum I-picture size is 1 Mbyte, 20bits are required as the bit width. Meanwhile, the I-picture occursapproximately every 0.5 seconds, and the size of the EP_map becomesgreater in accordance with the time length of the video stream. To thecontrary, the reading from the optical disc is performed in units ofreading, such as sectors and ECC blocks. In view of such a reality, theaccuracy as high as the byte-by-byte recording is unnecessary.Therefore, the recording device 200 represents the I-picture size usingthe number of the ECC blocks. The ECC (Error Correction Code) block is adata unit for Reed-Solomon coding. With the ECC block, it is possible todetect a read error occurred in the block, and it is assured that someread errors can be restored to correct data.

In the case of the BD-ROM, the ECC block length is 64 k bytes. Theplayback device 300 reads data from each ECC block, and transfers onlyrequired data included in the ECC block to a memory, a decoder, and soon. Even if the I-picture size is smaller than the ECC block, or even ifthe I-picture size is as large as the ECC block, the size of the dataread from the recording medium stay constant, because the data is readfrom the recording medium in units of the ECC blocks.

Based on such a circumstance, the I-picture size to be stored into theEP_map is recorded in units that are meaningful at the time of reading,such as units of ECC block sizes. The maximum I-picture size “1 Mbyte”can be represented as the maximum number of ECC blocks “20”, where theECC block size is 64 k byte (1 M byte<64 k byte×20).

The value “20” as the number of the ECC blocks can be represented by 5bits. In this way, the data size of the EP_map can be reduced.

The following describes an optimization performed for further shorteningthe bit width that represents the I-picture size. The I-picture sizedepends on characteristics of original images to be compressed and analgorithm used for the compression. However, although the sizes of theI-pictures vary to some extent, it can be concentrated within a certainrange if the transfer rate assigned to the video stream is fixed, to 24Mbps for instance. FIG. 3 is an example graph showing occurrence ratesof I-pictures of a certain content, by classifying the I-picturesaccording to their respective ECC block sizes. Each original image has atype, such as an image of nature and an animation, and each type has adifferent characteristic. The bit rate to be assigned to each type isdifferent as well. Therefore, the I-picture sizes on the graph of FIG. 3showing the occurrence rates are distributed over different ranges.However, it is empirically known that the I-picture sizes are almostalways distributed in the same manner (the normal distribution).

In the upper graph of FIG. 3, the vertical axis represents the number ofoccurrences of the I-picture, and the horizontal axis represents thesize of the I-picture by the number of the ECC blocks. Note that thehorizontal axis represents the offset address (I_end) from the startaddress to the end address of the I-picture included in the multiplexedstream.

Apart from the case where pieces of image data of different types, suchas an image of nature and an animation, are compressed together as onevideo stream, the original images that are to be compressed into onevideo stream usually have a similar characteristic. Therefore, thenumber of the occurrences on the graph is almost always concentratedwithin a certain range in terms of the horizontal axis. In FIG. 3, forinstance, most of the I-picture sizes are concentrated within the rangewhere the number of the ECC blocks is between 8 and 9.

The I-picture does not show the difference between reference images, andalways includes pixels for one frame. Therefore the I-picture size doesnot become very small, and there is few I-picture that includes not morethan seven ECC blocks. Also, apart from some hard-to-compress images,the I-picture size hardly becomes extremely large, because one algorithmis used for the compression.

Given these factors, to represent the I-picture size by a narrower bitwidth, the ranges where the occurrence rate of the I-picture size (thenumber of ECC blocks) is low are integrated together, while a resolutionwithin a range where the occurrence rate is high is maintained. It isassumed in FIG. 3 that in the case where 24 Mbps of the transfer rate isassigned to the video stream for instance, the maximum I-picture size isthirty-two ECC blocks. For representing the number “32”, 5 bits arerequired. However, the I-picture size can be represented by 4 bits or 3bits by dividing the horizontal axis of the graph into 16 groups or 8groups, and representing the I-picture size by showing which group theI-picture belongs to.

Here, the bit width of 3 bits should be used effectively forrepresenting data. If all the I-pictures are 100 Kbytes or more, thereis no point in dividing the range between 0 and 90 Kbytes into smallerranges and representing each range by 3 bits. Such a representationshould be avoided.

When the minimum I-picture size in the graph is 92276 bytes, the sizecan be represented by the number of ECC blocks as 1.4 ECC blocks, whichis nearly equal to 92276 bytes, and 0≦1.4 ECC blocks<2 ECC blocks istrue. Therefore, the playback device 300 is required to read at leasttwo ECC blocks. Accordingly, the assignment is performed so that theplayback device 300 reads at least two ECC blocks.

The broken lines shown in FIG. 3 are borders between the groups of theI-picture size. As shown in FIG. 3, the I-picture size is classified bythe borders which represent the sizes of 0, 2, 4, 6, 9, 14 and 20 ECCblock(s) respectively. Seven values “001b” to “111b” are assigned to therespective borders. The lower graph in FIG. 3 shows such an assignment.The value “001b” is assigned to the border representing 0 ECC block, thevalue “010b” is assigned to the border representing 2 ECC blocks, thevalue “011b” is assigned to the border representing 4 ECC blocks, thevalue “100b” is assigned to the border representing 6 ECC blocks, thevalue “101b” is assigned to the border representing 9 ECC blocks, thevalue “110b” is assigned to the border representing 14 ECC blocks, andthe value “111b” is assigned to the border representing 20 ECC blocks.In this embodiment, the 3-bit value “000b” is not assigned to anyborder, because “000b” is desired to be used for representing an invalidentry.

As described above, the I-picture size is represented by the values 001bto 111b assigned to the borders, and these values are described in theI_end. For instance, if the I-picture size of an I-picture is 65536bytes which corresponds to the size of one ECC block, the size belongsto the range between 0 and 2 in FIG. 3. The I-picture size isrepresented by describing the value “001b (=1)” in the I_end.

If the I-picture size of another I-picture is 196608 bytes whichcorresponds to the size of three ECC blocks, the size belongs to therange between 2 and 4 in FIG. 3. The I-picture size is represented bydescribing the value “010 (=2)” in the I_end. In this way, the I_end foreach entry is described to create the EP_map.

This is end of the description of the recording device 200.

Playback Device 300

The playback device 300 plays back the AVClip recorded on the recordingmedium. If the recording medium is an optical disc, random access isavailable. However, the seek time is longer than the case of HDDs andsemi-conductor memories. This is the principal factor responsible fordegradation in response time. For the cases where seeks are frequentlyperformed, such as cases of performing special playbacks, it isimportant not to perform redundant seeks and not to read unnecessarydata. Therefore, the playback device 300 performs the playback at doublespeed by playing back only I-pictures continuously with reference to agroup of entries included in the entry map. The information about thelocations and sizes of the I-pictures are used very effectively at thetime of such a playback at double speed. The playback device 300 assumesthat the values 000b to 111b are assigned to I-picture sizes as shown inthe lower graph of FIG. 3, and determines the amount of the data, whichthe playback device 300 reads from the recording medium, based on thevalues. Here, the amount of the data is represented by each ofdistribution ranges, which are obtained by dividing the occurrencedistribution of the I-picture sizes according to the borders as shown inFIG. 3. FIG. 4A to 4D show how the playback device 300 interprets theI_end.

For instance, if the 3-bit value representing the I_end is “001b” asshown in FIG. 4A, “001b” is assigned to the range of I-picture sizewhere “the number of the ECC blocks=0 to 2”, and therefore, the value“0” is interpreted as the lower limit of the amount of the data that theplayback device 300 reads. Meanwhile, the upper limit of the amount is“the number of the ECC blocks=2” that corresponds to the 3-bit value“001b+1b”, that is “010b”. Accordingly, the I-picture size is equal toor more than 0 and less than 2. The playback device 300 reads two ECCblocks from the start address of the I-picture.

If the 3-bit value representing the I_end is “010b” as shown in FIG. 4B,“010b” is assigned to the range of I-picture size where “the number ofthe ECC blocks=2 to 4”, and therefore, the value “2” is interpreted asthe lower limit of the amount of the data that the playback device 300reads. Meanwhile, the upper limit of the amount is “the number of theECC blocks=4” that corresponds to the 3-bit value “010b+1b”, that is“011b”. Accordingly, the I-picture size is equal to or more than 2 andless than 4. The playback device 300 reads four ECC blocks from thestart address of the I-picture.

If the 3-bit value representing the I_end is “011b” as shown in FIG. 4C,“011b” is assigned to the range of I-picture size where “the number ofthe ECC blocks=4 to 6”, and therefore, the value “4” is interpreted asthe lower limit of the amount of the data that the playback device 300reads. Meanwhile, the upper limit of the amount is “the number of theECC blocks=6” that corresponds to the 3-bit value “011b+1b”, that is“100b”. Accordingly, the I-picture size is equal to or more than 4 andless than 6. The playback device 300 reads six ECC blocks from the startaddress of the I-picture.

If the 3-bit value representing the I_end is “110b” as shown in FIG. 4D,“110b” is assigned to the range of I-picture size where “the number ofthe ECC blocks=14 to 20”. Therefore, the value “14” is interpreted asthe lower limit of the amount of the data that the playback device 300reads. Meanwhile, the upper limit of the amount is “the number of theECC blocks=14” that corresponds to the 3-bit value “110b+1b”, that is“111b”. Accordingly, the I-picture size is equal to or more than 14 andless than 20. The playback device 300 reads twenty ECC blocks from thestart address of the I-picture.

As described above, the recording device 200 and the playback device 300determine the I-picture size based on the value represented by 3-bitvalue.

In FIG. 3, it is assumed that the assigned bit rate is 24 Mbps. In thecase where a plurality of video streams are recorded on the recordingmedium and the bit rate varies widely for each video stream, it isimpossible to represent the optimum data amount for the reading by a3-bit width. FIG. 5 shows the occurrence rates of I-pictures in the casewhere the fluctuation band of assigned bit rates is wide. The full lineis the same as that shown in FIG. 3, which represents the occurrencerates when the average bit rate is 24 Mbps. The broken lines show theoccurrence rates when the average bit rate is 1 Mbps and 48 Mbps. Thepeaks of the occurrence rates are within the ranges represented by“001b” and “111b” respectively. Here, the lower limit of the rangerepresented by “111b” is 20 ECC blocks. However, its upper limit is notdefined. Therefore, to read enough I-pictures belonging to the range“111b”, it is required to read extra ECC blocks, for instance 40 or 50ECC blocks. This is the worst case, because the amount of the data to beread becomes too large. Therefore, if such a worst case occursfrequently, the reading efficiency is to be extremely degraded.

The structure of the recording device 200 is designed to avoid such aworst case. The following describes the recording device 200 accordingto the present invention, with reference to FIG. 6. FIG. 6 shows theinternal structure of the recording device 200. As shown in FIG. 6, therecording device 200 includes a video encoder 1, a multiplexer 2, awrite buffer 3, a drive unit 4, a statistical memory 5, an analysis unit6 and a scenario memory 7.

The video encoder 1 encodes an input video signal to obtain a videostream, and outputs the video stream. When a transport stream that ispreviously encoded is input into the recording device 200, the videoencoder 1 may transcode the transport stream, or may output thetransport stream as it is to the multiplexer 2.

The multiplexer 2 multiplexes a video stream output from video encoder 1and other elementary streams, such as a graphics stream and an audiostream to obtain an AVClip, and outputs the AVClip to the write buffer3. At the time of the multiplexing, the multiplexer 2 detects the sizesof I-pictures included in the AV clip, and writes the detection result,that is the I-picture sizes, into the statistical memory 5 as themeasured values. This detection includes a measuring operation formeasuring the number of TS packets including the TS packet that storesthe beginning of the I-picture to the TS packet that stores the end ofthe I-picture, and a reading operation for reading the I-picture sizefrom the I-picture size field. Also when a transport stream that ispreviously encoded is input into the recording device 200, themultiplexer 2 detects the addresses and the sizes of the I-pictures, andwrites the detection result, that is the measured values, into thestatistical memory 5.

Here, the measured values, which are output by the multiplexer 2,represent the sizes of I-pictures in the transport stream format, and donot represent the sizes of the I-pictures included in the video stream.This means that the total data size of the TS packets including the TSpacket that stores the beginning of the I-picture to the TS packet thatstores the end of the I-picture is represented as the “I-picture size”.Therefore, in the case where a TS packet that includes a part of otherelementary stream, such as an audio stream and a graphics stream, existsbetween the TS packet that stores the beginning of the I-picture and theTS packet that stores the end of the I-picture, the total of the size ofsuch a TS packet and the original I-picture size is to be output as themeasured value representing the I-picture size.

When a transport stream that is previously encoded is input into therecording device 200, the multiplexer 2 may extract only a requiredelementary stream and convert the elementary stream into a partialtransport stream in which PSI/SI packets are modified. The PSI/SIpackets are packets that include structure information of a programdefined in the MPEG standard and the digital broadcasting standards.

The drive unit 4 sequentially writes AVClips written into the writebuffer 3 into the recording medium 100.

The statistical memory 5 is a memory into which a plurality of measuredvalues output from the multiplexer 2 are to be written.

The analysis unit 6 analyzes the plurality of the measured values, whichare written into the statistical memory 5, to generate an I_end_tableand a group of entries in the scenario memory 7. The I_end_table is aconstituent of the EP map. In this embodiment, the EP map is generatedfrom the I_end_table and the group of the entries. The analysis unit 6records the generated EP_map on the recording medium.

FIG. 7 is a flowchart showing a procedure performed by an analysis unit6 for creating an EP_map. The analysis unit 6 waits for the multiplexingto finish (Step S1), and when the multiplexing finishes, the analysisunit 6 classifies the measured values into seven groups, namely Gr(1) toGr(7) (Step S2). Then the analysis unit 6 represents the minimumI-picture size in each of Gr(1) to Gr(7) by the ECC block size, therebydetermines the lower limit of the amount of the data to be read for eachof Gr(1) to Gr(7) (Step S3). The analysis unit 6 creates an I_end_tableby assigning the group numbers of Gr(1) to Gr(7) to the lower limitsrespectively (Step S4).

Next, the analysis unit 6 creates the group of the entries. The analysisunit 6 obtains the I_end by representing, with use of the 3-bit valuethat represents the group number, the I-picture size included in eachmeasured value (Step S5). The analysis unit 6 obtains the group of theentries for I-pictures by associating the obtained I_end with theI_start that represents the I-picture address (Step S6).

The table obtained in Step S4 is called the I_end_table. The I_end_tableis differently distributed for each stream to be compressed. Therefore,it is preferable that the I_end_table can be switched from one toanother for each stream, and each file. Therefore, upon creating thegroup of the entries and the I_end_table through the above-describedprocedure, the analysis unit 6 creates the EP_map from the group of theentries and the I_end_table, and records the EP_map in association withthe AVClip on the recording medium (Step S7).

The creation of the group of the entries is performed in the followingmanner. The I_end_table is created in the above-described manneraccording to the distribution characteristic of the occurrence rates ofthe I-picture sizes, and written into an area of the EP_map which isreserved for defining the I_end_table. Accordingly, it becomes possibleto switch the I_end_table, which defines the I_end used for surelyreading the I-picture, for each stream and each file.

When the I-picture sizes obtained by analyzing the AV clip aredistributed as FIG. 3 shows, the I_end should be set such that thenumber of the I-pictures are distributed equally in each range of theI-picture size. The equalization can be realized by analyzing the sizesof all the I-pictures (the number of the I-pictures is N), sorting thesizes of the I-pictures in ascending order, classifying the I-picturesizes into groups based on the total number of the I-pictures divided by7, and assigning a multiple of the ECC block size that is more than andnearest to the divided number to each group.

A flowchart of FIG. 8 shows such a procedure. FIG. 8 is a flowchartshowing a procedure for classifying measured values.

Firstly, the measured values are sorted in ascending order of theI-picture sizes (Step S11). Data strings obtained by the sorting areclassified into groups as follows (Step S12):

1^(st) to 1/7×N−1^(th)=>Gr(1) 1/7×N^(th) to 2/7×N−1^(th)=>Gr(2)2/7×N^(th) to 3/7×N−1^(th)=>Gr(3) 3/7×N^(th) to 4/7×N−1^(th)=>Gr(4)4/7×N^(th) to 5/7×N−1^(th)=>Gr(5) 5/7×N^(th) to 6/7×N−1^(th)=>Gr(6)6/7×N^(th) to N^(th)=>Gr(7).

As a result, the groups Gr(1) to Gr(7) are obtained. If Gr(3) is 5.3 ECCblocks for instance, an integer 6, which is more than and nearest to5.3, should be assigned to Gr(3).

In this example, thirty-two ECC blocks (5 bits) are classified intoseven groups. However, the number of the groups and so on is not limitedto this as long as the number is not larger than the example.

The detail of the classification performed in Step S12 is described nextwith reference to a specific example shown in FIG. 9.

The table on the left of FIG. 9 is the measured values. The table on theright is the result of sorting the measured values. The braces in thefigure represent the classification into seven groups, namely Gr(1) toGr(7).

By such a classification, the 1^(st) measured value “63520” to the1/7×N−1^(th) measured value are classified into Gr(1), the 1/7×N^(th)measured value “92276” to the 2/7×N−1^(th) measured value are classifiedinto Gr(2), the 2/7×N^(th) measured value “124322” to the 3/7×N−1^(th)measured value are classified into Gr(3), and the 6/7×N^(th) measuredvalue to the N^(th) measured value are classified into Gr(7).

FIG. 10A to 1C show the detail of the conversion performed forconverting the I-picture size into the number of the ECC blocks. Thequotient of the I-picture size divided by the ECC block size is to beregarded as the number of the ECC blocks (FIG. 10A).

However, in this case if the I-picture size is smaller than the ECCblock size, the number of the ECC blocks becomes “0”. Furthermore, ifthe I-picture is not aligned with the border between the ECC blocks, itbecomes impossible to read sufficient data. Here, if the I-picture is“aligned”, it means that the I-picture is properly arranged in aposition starting from the border between the ECC blocks. If theI-picture size is as large as the two ECC blocks, and I-picture isarranged in a position starting from the middle of the ECC block, a partof I-picture might not be read properly only by reading two ECC blocks.FIG. 10C shows a case in which the I-picture is not aligned with theborder between the ECC blocks. In this embodiment, assuming the cases ofFIGS. 10B and 10C, the formula for converting the I-picture size intothe number of the ECC blocks is defined as follows:The number of ECC blocks=I-picture size/ECC block size+1.

The addition “+1” means that one extra ECC block is to be included inthe count. Accordingly, it becomes possible to read sufficient ECCblocks even in the case of FIG. 10B, where the I-picture size is smallerthan the ECC block size, and in the case of FIG. 10C, where theI-picture is not aligned with the border between the ECC blocks.

FIG. 11 shows the EP_map that is obtained by integrating the I_end_tableand the group of the entries. In FIG. 11, the I_end_table is integratedinto the EP_map as an information element, namely I-picture informationfor the EP_map (EP_map_GI). Therefore, the playback device 300 canproperly interpret the I_end (3-bit value) by referring to theI_end_table in the EP_map_GI.

The internal structure of the recording device 200 is described above.The internal structure of the playback device 300 according to thepresent invention is described next. FIG. 12 shows the internalstructure of the playback device 300. The playback device 300 includes adrive unit 11, a read buffer 12, a demultiplexer 13, a video decoder 14,a scenario memory 15, a conversion unit 16 and a playback control unit17.

The drive unit 11, to which the recording medium having the EP_map andthe AVClip recorded thereon is inserted, performs a reading and awriting of data on the recording medium.

The read buffer 12 is a buffer used for temporally storing the AVClipread from the drive unit 11.

The demultiplexer 13 demultiplexes the AVClip to obtain the videostream, the graphics stream, and the audio stream.

The video decoder 14 decodes the video stream obtained through thedemultiplexing by the demultiplexer 13 to output a video.

The scenario memory 15 is a memory from which the I_end_table and thegroup of entries are read.

The conversion unit 16 converts the 3-bit I_end data described in eachentry included in the group of the entries into the amount of data to beread. When a value “xxx” is described as the I_end in an entry in thegroup of the entries, the conversion unit 16 reads a number of ECCblocks “y” associated with the value “xxx” from the I_end_table, andconverts the number “y” into the lower limit of the amount of reading.Furthermore, the conversion unit 16 reads a number of ECC blocks “z”associated with the value “xxx+1” from the I_end_table, and converts thenumber “z” into the upper limit of the amount of reading. The I-picturesize is equal to or more than “y” and less than “z”. Accordingly, thesize of data that the drive unit 11 needs to read is “z” ECC blocksbeginning from the I_start. Here, if the value “xxx” is “001b”, thenumber “0” associated with “000b” in the I_end_table is converted intothe lower limit of the amount of reading. The number “2” associated with“010b” (=xxx+1) is converted into the upper limit of the amount of thereading. As a result, the I-picture size satisfies:0 ECC block≦I-picture size<2 ECC blocks.

Therefore, it is required to read two or more ECC blocks for reading theI-picture in full measure.

That is to say, the playback device 300 is required to read the datahaving the size equal to or more than the maximum I-picture sizedescribed, for each I_end, in the I_end_table.

The playback control unit 17 instructs the drive unit 11 to read a rangebeginning from the I-picture address described in the I_start andincluding more than z ECC blocks such that the I-picture is providedfrom the recording medium to the decoder.

As described above, the first embodiment enables each of the I-picturesizes to be represented by a small amount of information and a smallnumber of bits, by indirectly referring to the I_end_table thatclassifies the sizes into the groups. Therefore, it becomes possible tosuppress the number of the bits required for representing informationwhich frequently occurs, such as information for each I-picture.

The Second Embodiment

In the first embodiment, the playback device 300 integrates theI_end_table as an information element of the EP_map_GI into the EP_map.However, in the second embodiment, it is disclosed that the I_end_tableis separated from the EP_map. An identifier (I_end_table_id) is added tothe I_end_table for identifying each I_end_table separated from theEP_map. A reference value (I_end_table_id_ref) used for referring to theI_end_table is included in the EP_map_GI by way of compensation for theseparation.

FIG. 13 shows the data structure of the EP_map according to the secondembodiment. The reference value (I_end_table_id_ref) is described in theEP_map_GI, and therefore the playback control unit 17 according to thesecond embodiment reads the I_end_table_id_ref from the EP_map_GI, andinterprets the 3-bit value I_end using the I_end_table that correspondsto the read I_end_table_id_ref out of I_end_tables that are previouslydefined. The setting for each I_end_table may be previously defined incommon, or may be recorded on the recording medium.

By separating the I_end_table from the EP_map, it becomes possible for aplurality of AVClips to share one I_end_table. This reduces the size ofthe EP_map.

As described above, in the second embodiment, the EP_map can be definedeasily, because if the characteristic of the original image of the moviecontent and the characteristic of the encoder are within narrow rangesrespectively, it is unnecessary to set the I_end_table every time. Onlythe I_end_table that is to be referred is required to be specified. Adefault I_end_table may be set in case the reference value is invalid.

The Third Embodiment

The third embodiment relates to a modification for recording theI_end_table separated from the EP_map, just as the second embodiment.Additional information is set up at the time of recording theI_end_table. This additional information represents what encoding methodthe video stream corresponding to the I_end_table is encoded by. If thevideo stream is encoded by the MPEG2-video encoding, the additionalinformation indicating the MPEG2-video encoding is to be described inthe I_end_table, and if the video stream is encoded by the MPEG-AVCencoding, the additional information indicating the MPEG-AVC encoding isto be described in the I_end_table.

FIG. 14 shows the entry map according to the third embodiment. In FIG.14, the I_end_table#1 includes the additional information for theMPEG4-AVC, and the I_end_table#2 includes the additional information forthe MPEG2-video.

Meanwhile, at the time of the playback, the playback control unit 17detects the encoding method used for the AVClip that is to be playedback, reads out the I_end_table corresponding to the detected encodingmethod out of a plurality of I_end_tables that are previously defined(or recorded on the recording medium), and interprets the 3-bit value ineach entry with reference to the read I_end_table.

As described above, according to the third embodiment, if the occurrencerates are almost the same when the attribute of the stream, such asMPEG-2 and MPEG4-AVC, is the same, it becomes possible to previouslydefine I_end_table for each stream attribute. This reduces the number ofthe I_end_tables. Also, it becomes possible to determine whichI_end_table should be referred to, without using the reference value forthe I_end_table. This makes the process performed by the playback device300 simple.

Note that in addition to the encoding method, the average bit rate ofthe stream, the maximum bit rate, the category that the content usingthe stream belongs to and so on, or their combination may be used forswitching the I_end_table to be referred according to the attribute ofthe stream. Furthermore, a default I_end_table, which is referred to inthe case where no attribute information exists, may be-prepared.

The Fourth Embodiment

In the first embodiment, the I-picture sizes are represented by numberof bytes and they are classified into groups. However, in the fourthembodiment, the I-picture sizes included in the measured values arepreviously represented by the number of the block sizes to be classifiedinto groups.

FIG. 15 is a flowchart showing the procedure for the classificationaccording to the fourth embodiment.

In Step S14, each I-picture size is represented by the number of the ECCblocks. In Step S14, the measured values are sorted in ascending orderof the numbers of the ECC blocks. By representing the I-picture size bythe number of the ECC blocks, the sizes less than 64 K byte are to beomitted as fractions, and many picture sizes are to be classified onegroup.

In Step S16, the sorted measured values are classified into groupsaccording to the following rule.

1^(st) to 1/8×N−1^(th)=>Gr(1) 1/8×N^(th) to 2/8×N−1^(th)=>Gr(2)2/8×N^(th) to 3/8×N−1^(th)=>Gr(3) 3/8×N^(th) to 4/8×N−1^(th)=>Gr(4)4/8×N^(th) to 5/8×N−1^(th)=>Gr(5) 5/8×N^(th) to 6/8×N−1^(th)=>Gr(6)6/8×N^(th) to 7/8×N−1^(th)=>Gr(7) 7/8×N^(th) to N^(th)×>Gr(8)

As a result, the eight groups, namely Gr(1) to Gr(8), are obtained.

In the first embodiment, the measured values are classified into sevengroups. However, in the fourth embodiment, they are classified intoeight groups. Therefore, the I_end uses eight values, namely “000b” to“111b” to represent the I-picture size. In the following embodiments,the descriptions are based on the fact that the measured values areclassified into eight groups.

FIG. 16A shows the number of ECC blocks representing the I-picture sizeand occurrence rates of the I-pictures having the size in relation toeach other. FIG. 16B shows the result of the group classificationperformed in Step S16 in FIG. 15.

The I-pictures including eight to eleven ECC blocks frequently occur.Therefore, the measured values represented by “the number of the ECCblocks=8”, “the number of the ECC blocks=9”, “the number of the ECCblocks=10” and “the number of the ECC blocks=11” are classified intoGr(2), Gr(3), Gr(4) and Gr(5) respectively.

The I-pictures including twelve to thirteen ECC blocks and theI-pictures including fourteen to sixteen ECC blocks do not occurfrequently. Therefore, the occurrence rates of the valued measuresincluded in two to three ECC block groups are integrated together. Themeasured values represented by “the number of the ECC blocks=12 to 13”are classified into Gr(6), and the measured values represented by “thenumber of the ECC blocks=14 to 16” are classified into Gr(7).

The I-pictures including one to seven ECC blocks are not rare, and theyare therefore classified into Gr(1). The I-pictures including seventeento thirty-two ECC blocks are not rare as well, and they are thereforeclassified into Gr(8). The total number of occurrences is at the samelevel in each group.

Each I-picture size is represented by the number of the ECC blocks, andmany measured values have the same I-picture size. Therefore, in thisembodiment, the measured values are classified into groups so that thetotal number of occurrences in each group becomes almost at the samelevel. For instance, the total numbers of occurrences are 992, 743, 790,865, 829, 1268, 996 and 704 respectively.

As described above, the fractions of the ECC block sizes less than oneECC block is not required to be considered in the fourth embodiment, andthe measured values can be processed immediately.

The Fifth Embodiment

In the first to fourth embodiments, the classification is performedbased on the I-picture size. However, in the fifth embodiment, the rangethat the I-picture size covers in the coordinate system that shows theoccurrence distribution is equally divided into groups. FIG. 17A showsthe coordinate system showing the occurrence distribution. The verticalaxis represents the occurrence rates of the I-pictures, and thehorizontal axis represents the I-picture sizes by the numbers of the ECCblocks. The I-picture sizes represented by the horizontal axis indicateup to thirty-two ECC blocks.

In the fifth embodiment, such a range of the I-picture sizes are equallydivided into groups. The sign “<−>” in FIG. 17A shows how the range ofthe I-picture sizes is divided. As shown in FIG. 17A, the number of ECCblocks 1 to 4 are classified into Gr(1), 5 to 8 are classified intoGr(2), 9 to 12 are classified into Gr(3), 13 to 16 are classified intoGr(4), 17 to 20 are classified into Gr(5), 21 to 24 are classified intoGr(6), 25 to 28 are classified into Gr(7), and 29 to 32 are classifiedinto Gr(8). As a result of such a classification, the measured valuesshown in FIG. 17A are divided into eight groups as shown in FIG. 17B.

Note that as the I-picture sizes are divided into groups so that thenumbers of the ECC blocks are distributed equally, the fifth embodimentis disadvantageous in that the resolution within the range in which theoccurrence rate is high is decreased.

The Sixth Embodiment

The sixth embodiment is an improvement upon the fifth embodiment. How tohandle the singularities on the horizontal axis is improved. Extremelylarge picture sizes are sometimes found in the measured values, and suchpicture sizes are called singularities.

FIG. 18 is a coordinate system showing the occurrence distribution, justas FIG. 17. The I-picture including twenty-seven ECC blocks and theI-picture including thirty ECC blocks respectively correspond tooriginal images that are hard to be compressed. These large sizes areprobably due to low compression efficiency. Usually, such large sizesrarely occur. Therefore, these singularities are separated from othersat the time of the classification. In FIG. 18, for instance, theI-pictures whose sizes are twenty-five or more ECC blocks are separatedfrom others. Reading of such large I-pictures usually requires a lot oftime at the time of the continuous playback. It is highly possible thatthey are not suitable for the high-speed playback. A smooth high-speedplayback can be realized by skipping such I-pictures at the time of thehigh-speed playback.

In the example shown in FIG. 18A, the I-pictures including twenty-fiveor more ECC blocks are ruled out as the singularities, and classifiedinto one group. Then, the other I-picture sizes are classified intoseven groups. FIG. 18B is an example classification with considerationof the singularities. As shown in FIG. 18B, the number of ECC blocks 1to 7 are classified into Gr(1), 8 to 9 are classified into Gr(2), 10 isclassified into Gr(3), 11 is classified into Gr(4), 12 to 13 areclassified into Gr(5), 14 to 15 are classified into Gr(6), and 16 to 24are classified into Gr(7). The singularities including twenty-five ormore ECC blocks are classified into Gr(8). As a result of such aclassification, the measured values shown in FIG. 18A are divided intoeight groups as shown in FIG. 18B.

The singularities to be skipped at the time of the high-speed playbackare classified into Gr(8), and therefore the fluctuation band betweenGr(1) to Gr(7) becomes narrow.

As described above, the I-picture sizes are equally assigned to the3-bit values.

Note that the singularities may be determined according to the readingperformance of the drive, not to the occurrence rates. For instance, ifthe maximum bit rate is 40 Mbps, the size of one picture can not be 5Mbytes, which is data for one second. Therefore, the size “5 Mbytes” maybe used as the threshold.

The Seventh Embodiment

The seventh embodiment discloses an improvement of the classification ofthe range that the I-picture size covers. In the fifth embodiment, theI-picture sizes are equally divided into groups. However, in the seventhembodiment, the I-picture sizes are divided so that large I-picturesizes are classified into more groups. In other words, in the fifthembodiment, the range that the I-picture sizes cover is equally dividedinto groups each including a certain number of ECC blocks, but in theseventh embodiment, the range is unequally divided, which means that thesmaller the I-picture sizes become, the wider the range of the groupbecomes, and the larger the I-picture sizes become, the narrower therange of the group becomes.

FIG. 19A shows how the range of the I-picture sizes is classified. AsFIG. 19A shows, the number of ECC blocks 4 to 11 are classified intoGr(1), 12 to 15 are classified into Gr(2), 16 to 19 are classified intoGr(3), 20 to 21 are classified into Gr(4), 22 to 23 are classified intoGr(5), 24 is classified into Gr(6), 25 is classified into Gr(7), and 26is classified into Gr(8). FIG. 19B shows the correlation among theranges of the groups. As shown in FIG. 19B, the range of Gr(2) is 1/2 ofthe range of Gr(1), and the range of Gr(3) is also 1/2 of the range ofGr(1). The range of Gr(4) is 1/4 of the range of Gr(1), the range ofGr(5) is 1/4 of the range of Gr(1), the range of Gr(6) is 1/8 of therange of Gr(1), and the range of Gr(7) is 1/8 of the range of Gr(1). Asa result of such a classification, the measured values are classifiedinto eight groups as shown in FIG. 19C.

The range of the group is narrow where the I-picture sizes included inthe group are large. Therefore, the larger the I-picture size becomes,the error between the reading amount of the data and the actualI-picture size becomes smaller. This improves the efficiency in thereading of the I-pictures.

As described above, the seventh embodiment can improve the efficiency inthe reading of the I-pictures by classifying large I-pictures into moregroups than small I-pictures.

The Eighth Embodiment

In the eighth embodiment, a plurality of classification patterns, whichare used for classifying the measured values into eight groups, aregenerated, and the most suitable one out of the patterns is to beselected.

FIG. 20 is a flowchart according to the eighth embodiment, showing aprocedure for classifying the measured values. In this flowchart, theplurality of the classification patterns, which are used for classifyingthe measured values into seven groups, are firstly generated (Step S21).Then, a standard deviation of each pattern is calculated (Step S22) andthe measured values are classified into Gr(1) to Gr(8) based on thepattern whose standard deviation is the smallest (Step S23). The detailsof the procedure represented by the flowchart are described next withreference to specific examples shown in FIG. 21.

FIG. 21 shows two example patterns among the plurality of theclassification patterns generated in Step S21. The upper pattern 1 isgenerated in the same manner as the third embodiment. The lower pattern2 is generated in the same manner as the fifth embodiment.

The standard deviation of each pattern is calculated. In this case, thestandard deviation of the upper pattern 1 is 183.03, and the standarddeviation of the lower pattern 2 is 1157.8. The pattern whose standarddeviation is the smallest is to be selected. Between the examples inFIG. 21, the pattern 1 is to be selected. Then the measured values areclassified into eight groups based on the selected pattern.

As described above, the plurality of the classification patterns, whichare used for classifying the measured values into eight groups, aregenerated in the eighth embodiment, and the measured values areclassified on the basis of the classification pattern whose standarddeviation is the smallest. Therefore, almost the same numbers of themeasured values are to be included in each group. Accordingly, thereading amount can be properly determined based on the 3-bit value.Also, it becomes possible to maintain the high resolution within a rangewhere the occurrence rate is high.

Note that in the case where the standard deviation is the same among theclassification patterns, the pattern in which the larger I-picture sizesare classified into more groups may be preferentially selected. To thecontrary, the pattern in which the smaller I-picture sizes areclassified into more groups maybe preferentially selected.

The Ninth Embodiment

The ninth embodiment relates to an improvement in which a speed rate ofthe playback device 300 is assigned to each digit of the 3-bit valuerepresenting the I-picture size. FIG. 22 shows examples of the assignedspeed rates. The values representing the I_end, such as 001b, 010b,011b, 100b, 101b, 110b, and 111b are assigned to the speed rates, suchas ×16, ×8, ×6, ×4, ×3, ×2, and ×1.

To realize such an assignment, the analysis unit 6 in the ninthembodiment performs classification of the measured values according tothe procedure shown in FIG. 23.

In step S31, the upper limit of the I-picture size for each speed rateis determined. Here, the upper limit is determined according to a rulethat the larger the speed rate is, the smaller the I-picture is, and thesmaller the speed rate is, the larger the I-picture size is.

For instance, in Step S32, the measured values are classified into thefollowing groups based on the upper limits for each speed rate:

The measured values that satisfy I-picture size<the upper limit for ×16speed=>Gr(1).

The measured values that satisfy I-picture size<the upper limit for ×8speed=>Gr(2).

The measured values that satisfy I-picture size<the upper limit for ×6speed=>Gr(3).

The measured values that satisfy I-picture size<the upper limit for ×4speed=>Gr(4).

The measured values that satisfy I-picture size<the upper limit for ×3speed=>Gr(5).

The measured values that satisfy I-picture size<the upper limit for ×2speed=>Gr(6).

The measured values that satisfy I-picture size<the upper limit for ×1speed=>Gr(7).

Finally, in Step S33, the I_end_table is created by assigning the upperlimits for the speed rates to 3-bit values that represent Gr(1) toGr(7).

The improvement of the recording device 200 according to the ninthembodiment is described above. The improvement of the playback device300 according to the ninth embodiment is described next.

Upon receiving a request for performing playback at a certain speed ratefrom the user, the playback device 300 identifies the 3-bit valuecorresponding to the requested speed rate. The playback device 300refers to only the entry having a value more than the identified 3-bitvalue, in order to read only the I-picture corresponding to the entryfrom the recording medium.

For instance, for performing ×4 speed playback, the playback device 300refers to the entry whose I_end is “100b”, and reads only the I-picturecorresponding to the entry. Then, the playback device 300 reads otherentries corresponding to higher speed rates, namely the entries whoseI_ends are “011b” (×6 speed), “010b” (×8 speed) and “001b” (×16 speed)respectively, and reads the I-pictures corresponding to those entriesfrom the recording medium.

As described above, when the high-speed playback is requested from theuser, the playback device 300 can read a suitable number of theI-pictures from the recording medium only by reading I-pictures whosesizes are described in the entries corresponding to the speed ratespecified by the user. Therefore, the playback device 300 can realizethe high-speed playback of suitable quality even if the drive unit islow-speed.

The Tenth Embodiment

In the seventh embodiment, the range that the I-picture sizes cover isunequally divided into groups so that compared to the width of Gr(1) asa criterion, the larger the I-picture sizes become, the narrower therange of the group becomes. In the tenth embodiment, the range of thegroup is narrowed by focusing attention on the number of the I-picturesto be included in one group.

For dividing the range based on the number of the I-pictures, themeasured values are sorted in ascending order of the I-picture sizesjust as shown in the first embodiment. The sorted measured values areclassified into groups as follows:

1^(st) to 1/2×N−1^(th)=>Gr(1) 1/2×N^(th) to 3/4×N−1^(th)=>Gr(2)3/4×N^(th) to 7/8×N−1^(th)=>Gr(3) 7/8×N^(th) to 15/16×N−1^(th)=>Gr(4)15/16×N^(th) to 31/32×N−1^(th)=>Gr(5) 31/32×N^(th) to63/64×N−1^(th)=>Gr(6) 63/64×N^(th) to 127/128×N−1^(th)=>Gr(7)127/128×N^(th) to N^(th)−>Gr(8)

FIG. 24 describes the function of the classification performed in thetenth embodiment.

The 1^(st) to 1/2×N−1^(th) values are classified into Gr(1), which meansthat 1/2 of the measured values are classified into Gr(1).

The 1/2×N^(th) to 3/4×N−1^(th) values are classified into Gr(2), whichmeans that 1/4 of the measured values are classified into Gr(2).

The 3/4×N^(th) to 7/8×N−1^(th) values are classified into Gr(3), whichmeans that 1/8 of the measured values are classified into Gr(3).

The 7/8×N^(th) to 15/16×N−1^(th) values are classified into Gr(4), whichmeans that 1/16 of the measured values are classified into Gr(4).

The 15/16×N^(th) to 31/32×N−1^(th) values are classified into Gr(5),which means that 1/32 of the measured values are classified into Gr(5).

The 31/32×N^(th) to 63/64×N−1^(th) values are classified into Gr(6),which means that 1/64 of the measured values are classified into Gr(6).

The 63/64×N^(th) to 127/128×N−1^(th) values are classified into Gr(7),which means that 1/128 of the measured values are classified into Gr(7).

The 127/128×N^(th) to N^(th) values are classified into Gr(8), whichmeans that the rest of the measured values are classified into Gr(8).

The number of the measured values included in Gr(1) to Gr(8) decreasesas the I-picture size increases, i.e. 1/2→1/4→1/8→1/32→1/64→1/128.

As described above, according to the tenth embodiment, the resolution ofthe I_end_table for the large I-pictures is improved, and therefore theresponse at the time of the special playbacks is improved.

Remarks

The above description by no means shows the implementation of allconfigurations of the present invention. Implementation of the presentinvention is still possible according to implementation ofconfigurations that carry out the following modifications (A), (B), (C),(D), . . . . The inventions pertaining to the claims of the presentapplication range from expanded disclosure to generalized disclosure ofthe plurality of embodiments disclosed above and the modifiedconfigurations thereof. The degree of expansion or generalization isbased on the particular characteristics of technical standards in thetechnical field of the present invention at the time of application.

-   (A) Although the I-picture size is represented by the number of the    ECC blocks in each embodiment, it may be represented by the number    of sectors (each sector is 2 k byte in the case of the BD-ROM), or    the number of packets included in the transport stream (each packet    is 192 bytes in the case of the BD-ROM). Furthermore, the I-picture    size may be represented by units of 192 bytes including Arrival Time    Stamp and TS packets, or by units of 32 Kbytes, which is the least    common multiple between 192 bytes and 2 Kbytes.-   (B) It is the size of the I-picture that is described in EP_map in    each embodiment. However, the I-picture is described as just an    example of the random access unit. (It is possible to display an    image by decoding only the random access unit.) The size of the    random access unit used in a method other than the MPEG2-video may    be described in the EP_map. For instance, the size of the IDR    picture used in the MPEG4-AVC (also called H.264 or JVT) may be    described.-   (C) It is acceptable to include bit rate information in the Clip    information and determine the meaning of the value of the I_end    based on the bit rate information. For instance, it is possible to    predefine I_end table for the case where the average bit rate is 10    Mbps, and use the value described in the I_end table multiplied by    1.5 as the I_end if the average bit rate of the AVClip is 15 Mbps.    In stead of the average bit rate, the maximum bit rate may be used    in the same way.-   (D) Only the size factors that will be the upper limits of the size    if the value of the I_end is valid (0, 2, 4, 6, 9, 14 and 20 in    FIG. 3) ma be described in the I_end_table.-   (E) Although he I_picture size is represented by the number of the    ECC blocks in each embodiment, it maybe represented by the number of    intersections of the ECC blocks. The number of the intersections of    the ECC blocks represents across how many ECC blocks the I-picture    is recorded. The number of the intersections can be a very useful    reference value for reading data from the disc.-   (F) The I-picture sizes may be classified based on proper values,    such as ECC block sizes, the number of occurrences of each ECC block    size maybe measured, and the sizes frequently occurs may be    classified into groups so that the resolution will be high, and the    sizes not frequently occur may be classified together into one    group. It may depend on the bit width of the I_end that how many    groups the sizes are classified into. Also, weighting may be    performed on the number of the occurrences of each ECC block size.-   (G) Although the recording device 200 and the playback device 300    are described as independent from each other in each embodiment, the    recording device 200 and the playback device 300 may be an    integrated recording/playback device.-   (H) The EP_map is navigation information defined in the BD-RE    standard and the BD-ROM standard. The data structure of the group of    the entries is described in each embodiment in accordance with the    BD-RE standard and the BD-ROM standard. However, the recording    medium used by the recording device 200 and the playback device 300    is not limited to optical disc, such as the BD-RE and the BD-ROM.    The recording medium may be any medium on which the video stream can    be recorded in accordance with the BD-RE standard or the BD-ROM    standard. The recording device 200 does not record video stream on    the BD-ROM directly, which means that the master BD-ROM disc is    created by forming an application format in accordance with the    BD-ROM standard on the hard disk. The BD-ROM is manufactured using    the master BD-ROM disc. From the point of view of such a    manufacturing method, it is possible to consider the hard disk as    the recording medium on which the recording device 200 records the    EP_map, and it is reasonable to consider the BD-ROM as the recording    medium which is played back by the playback device 300.-   (I) Although the playback device 300 in all of the embodiments    output AVClips recorded on a BD-ROM to a TV after decoding, the    playback device 300 may be structured from only a BD-ROM drive, and    the TV may be equipped with all of the other elements. In this case,    the playback device 300 and the TV can be incorporated into a home    network connected using IEEE1394. Also, although the playback device    300 in the embodiments is of a type used after connecting to a    television, integral display-playback devices are also applicable.    Furthermore, the playback device 300 may be only those parts of the    playback devices of the embodiments that perform essential parts of    the processing. Because these playback devices are all inventions    disclosed in the specification of the present application, acts    involving the manufacture of playback devices based on an internal    structure of the playback device 300 shown in embodiment 6 are    implementations of the inventions disclosed in the specification of    the present application.-   (J) Because of the information processing by computer programs shown    in the flowcharts being realized specifically using hardware    resources, computer programs showing the processing procedures in    the flowcharts form an invention in their own right. Although all of    the embodiments show embodiments that relate to the implementation    of computer programs pertaining to the present invention in an    incorporated form in the playback device 300, the computer programs    shown in the first embodiment may be implemented in their own right,    separate from the playback device 300.-   (K) Consider that the clement of “time” relating to the steps    executed in time-series in the flowcharts is a required item for    specifying the invention. If this is the case, then the processing    procedures shown by the flowcharts can be understood as disclosing    the usage configurations of the playback method. Execution of the    processing in the flowcharts so as to achieve the original objects    of the present invention and to enact the actions and effects by    performing the processing of the steps in time-series is, needless    to say, an implementation of the recording method pertaining to the    present invention.-   (L) Although digital streams recorded on a recording medium in the    embodiments are AVClips, the digital streams may be VOBs (Video    Objects) complying with a DVD-Video standard or a DVD-Video    Recording standard. VOBs are program streams compliant with    ISO/IEC13818-1 obtained by multiplexing video and audio streams.    Also, video streams in AVClips may be MPEG-4 format, WMV format, or    the like. Furthermore, audio streams may be a Linear-PCM format,    Dolby-AC3 format, MP3 format, MPEG-AAC format, or Dts format.-   (M) Movie works in the embodiments may be obtained by encoding    analog video signals broadcast by analog broadcast, or may be stream    data constituted from transport streams broadcast by digital    broadcast.

Also, contents may be obtained by encoding analog/digital video signalsrecorded on videotape. Furthermore, contents may be obtained by encodinganalog/digital video signals taken directly from a video camera.Alternatively, the contents may be digital copyrighted works distributedfrom a distribution server.

-   (N) The I_end_table may be defined not only in the EP_map, but also    in other management information.-   (O) Although the measured values are sorted in ascending order of    the sizes and classified into N groups in the first embodiment, the    measured values may be sorted in descending order of the seizes to    obtain measured data strings, and classified into N groups.-   (P) Although, in each embodiment, the information indicating the    assignment of the 3-bit data and the number of the ECC blocks is    recorded on the recording medium 100 as the I_end_table in a table    format, other format may be used as long as the information    indicating the assignment. For instance, the information may be a    correlation equation between the 3-bit data and the number of the    ECC blocks, or an offset.

Although the present invention has been fully described by way ofexamples with reference to the accompanying drawings, it is to be notedthat various changes and modifications will be apparent to those skilledin the art. Therefore, unless such changes and modifications depart fromthe scope of the present invention, they should be construed as beingincluded therein.

1. A recording device that records a video stream onto a recordingmedium, comprising: a detecting unit operable to detect sizes of Intrapictures included in the digital stream and output detected valuesincluding the Intra picture sizes; a classifying unit operable toclassify the detected values into N groups, wherein the classifying unitcomprises: a generating sub-unit operable to generate classificationpatterns used for classifying the detected values into N groups; and acalculating sub-unit operable to calculate a standard deviation of eachclassification pattern, and the classification by the classifying unitis performed based on one of the classification patterns with a smalleststandard deviation; an assigning unit operable to generate assignmentinformation which indicates distribution ranges of Intra picture sizesrespectively belonging to the N groups in a one-to-one association withnumerical values 1 to N respectively representing the N groups; and arecording unit operable to record an entry map onto the recording mediumin association with the assignment information, the entry maprepresenting each Intra picture included in the digital stream using thenumerical values 1 to N.
 2. The recording device of claim 1, wherein therecording unit records the assignment information onto the recordingmedium after adding an identifier to the assignment information, andrecords the entry map onto the recording medium after adding a referencevalue used for referring to the identifier to the entry map.
 3. Therecording device of claim 1, wherein the recording unit records theassignment information onto the recording medium after addinginformation indicating an encoding method used for encoding the digitalstream to the assignment information.
 4. A recording device that recordsa video stream onto a recording medium, comprising: a detecting unitoperable to detect sizes of Intra pictures included in the digitalstream and output detected values including the Intra picture sizes; aclassifying unit operable to classify the detected values into N groups,wherein the classification by the classifying unit is performed bydividing horizontal axis of a coordinate system into N ranges, thehorizontal axis and a vertical axis of the coordinate systemrepresenting the Intra picture sizes and numbers of occurrences thereofrespectively; an assigning unit operable to generate assignmentinformation which indicates distribution ranges of Intra picture sizesrespectively belonging to the N groups in a one-to-one association withnumerical values 1 to N respectively representing the N groups; and arecording unit operable to record an entry map onto the recording mediumin association with the assignment information, the entry maprepresenting each Intra picture included in the digital stream using thenumerical values 1 to N.
 5. The recording device of claim 4, wherein thehorizontal axis is equally divided into N ranges.
 6. The recordingdevice of claim 4, wherein the horizontal axis is divided so that widthsof the ranges decrease as the Intra picture sizes increase.
 7. Arecording device that records a video stream onto a recording medium,comprising: a detecting unit operable to detect sizes of Intra picturesincluded in the digital stream and output detected values including theIntra picture sizes; a classifying unit operable to classify thedetected values into N groups; an assigning unit operable to generateassignment information which indicates distribution ranges of Intrapicture sizes respectively belonging to the N groups in a one-to-oneassociation with numerical values 1 to N respectively representing the Ngroups; and a recording unit operable to record an entry map onto therecording medium in association with the assignment information, theentry map representing each Intra picture included in the digital streamusing the numerical values 1 to N, wherein each of the numerical values1 to N corresponds to a speed rate during a high-speed playback, andeach of the amounts of data to be read means an amount of data to beread during the high-speed playback.
 8. The recording device of claim 7,wherein the recording unit records the assignment information onto therecording medium after adding an identifier to the assignmentinformation, and records the entry map onto the recording medium afteradding a reference value used for referring to the identifier to theentry map.
 9. The recording device of claim 7, wherein the recordingunit records the assignment information onto the recording medium afteradding information indicating an encoding method used for encoding thedigital stream to the assignment information.
 10. A recording devicethat records a video stream onto a recording medium, comprising: adetecting unit operable to detect sizes of Intra pictures included inthe digital stream and output detected values including the Intrapicture sizes; a classifying unit operable to classify the detectedvalues into N groups; an assigning unit operable to generate assignmentinformation which indicates distribution ranges of Intra picture sizesrespectively belonging to the N groups in a one-to-one association withnumerical values 1 to N respectively representing the N groups; and arecording unit operable to record an entry map onto the recording mediumin association with the assignment information, the entry maprepresenting each Intra picture included in the digital stream using thenumerical values 1 to N, wherein the recording unit records theassignment information onto the recording medium after adding anidentifier to the assignment information, and records the entry map ontothe recording medium after adding a reference value used for referringto the identifier to the entry map.
 11. A recording device that recordsa video stream onto a recording medium, comprising: a detecting unitoperable to detect sizes of Intra pictures included in the digitalstream and output detected values including the Intra picture sizes; aclassifying unit operable to classify the detected values into N groups;an assigning unit operable to generate assignment information whichindicates distribution ranges of Intra picture sizes respectivelybelonging to the N groups in a one-to-one association with numericalvalues 1 to N respectively representing the N groups; and a recordingunit operable to record an entry map onto the recording medium inassociation with the assignment information, the entry map representingeach Intra picture included in the digital stream using the numericalvalues 1 to N, wherein the recording unit records the assignmentinformation onto the recording medium after adding informationindicating an encoding method used for encoding the digital stream tothe assignment information.
 12. A playback device comprising: a readingunit operable to read assignment information and an entry map includingentries, both corresponding to a digital stream to be played back, froma recording medium to a memory, the assignment information indicatingdistribution ranges of Intra picture sizes in one-to-one associationwith numerical values 1 to N; a converting unit operable to respectivelyconvert, based on the assignment information, values each having apredetermined bit width described in each entry into the distributionranges; and a playback unit operable to read Intra pictures included inthe digital stream based on the distribution ranges, wherein theassignment information is one of pieces of assignment informationrecorded on the recording medium, each piece of assignment informationhaving an identifier, the entry map includes reference values each usedfor referring to the identifier, the reading unit reads the assignmentinformation that corresponds to the reference value, and the conversionby the converting unit is performed based on the read assignmentinformation.
 13. A playback device comprising: a reading unit operableto read assignment information and an entry map including entries, bothcorresponding to a digital stream to be played back, from a recordingmedium to a memory, the assignment information indicating distributionranges of Intra picture sizes in one-to-one association with numericalvalues 1 to N; a converting unit operable to respectively convert, basedon the assignment information, values each having a predetermined bitwidth described in each entry into the distribution ranges; and aplayback unit operable to read Intra pictures included in the digitalstream based on the distribution ranges, wherein the assignmentinformation is one of pieces of assignment information recorded on therecording medium, each piece of assignment information includinginformation indicating an encoding method used for encoding the digitalstream corresponding to the assignment information, the reading unitreads the assignment information that corresponds to the encodingmethod, and the conversion by the conversion unit is performed based onthe read assignment information.
 14. A playback device, comprising: areading unit operable to read assignment information and an entry mapincluding entries, both corresponding to a digital stream to be playedback, from a recording medium to a memory, the assignment informationindicating distribution ranges of Intra picture sizes in one-to-oneassociation with numerical values 1 to N; a converting unit operable torespectively convert, based on the assignment information, values eachhaving a predetermined bit width described in each entry into thedistribution ranges; and a playback unit operable to read Intra picturesincluded in the digital stream based on the distribution ranges, whereinif a high-speed playback at a certain speed rate is requested by a user,the converting unit identifies an entry corresponding to the certainspeed rate among entries included in the entry map, and converts a valuedescribed in the identified entry into an amount of data to be read.